NEW YORK (CNNfn) - As of Thursday afternoon, more than 4,700 people were unaccounted for after Tuesday's terrorist attack aimed at New York's World Trade Center. Many of the missing include prominent executives from companies throughout the country.

Bill Meehan, market strategist Cantor Fitzgerald

Among the firms hardest hit by the destruction of the trade center's twin towers is bond broker Cantor Fitzgerald. According to a company site, 300 employees of the approximately 1,000 stationed on floors 101, 103, 104, and 105 in the North Tower have checked in safely. Excluded from the list is Bill Meehan, Cantor's market strategist and a frequent guest on CNNfn.

Also missing from the Cantor list are Fred Varacchi, president of the company's eSpeed unit, Doug Gartner, chief financial officer of Cantor and eSpeed, Pat Dwyer, head of equity sales, Michael Rothberg, head of program trading, and Tim Grazioso, Cantor's chief operating officer.

Thomas Burnett, COO Thoratec

A number of executives were passengers on the four hijacked planes. Thoratec (THOR: Research, Estimates) lost its chief operating officer, Thomas Burnett, as he was a passenger on United Airlines flight 93 bound for San Francisco. "He had originally been scheduled to take a later flight, but apparently booked the earlier flight at the last minute," said Thoratec's chairman and chief executive, Dr. Keith Grossman. "He was going home to be with his family."

Sun Microsystems (SUNW: Research, Estimates) said its director of software engineering, Phil Rosenzweig, was lost aboard American Airlines flight 11, which crashed into one of the World Trade Center's towers.

Akamai Technologies' (AKAM: Research, Estimates) co-founder and chief technology officer also passed aboard flight 11. "Danny was a wonderful human being," said Akamai's co-founder and chief executive, George Conrades. "He will be deeply missed by his friends at Akamai."

Daniel Lewin, co-founder, CTO Akamai Technologies

Raytheon (RTN: Research, Estimates) lost four executives in the plane crashes. Peter Gay, vice president of electronic systems, Stanley Hall, director of program management, David Kovalcin, senior mechanical engineer for electronic systems, and Kenneth Waldie, senior quality control engineer for electronic systems, were passengers on flights that crashed into the World Trade Center or the Pentagon. "Our hearts go out to the families, friends, and co-workers of those we have lost, and all who perished yesterday," Raytheon Chairman and CEO Dan Burnham said.

Edmund Glazer, the chief financial officer of MRV Communications (MRVC: Research, Estimates), was a passenger on American Airlines flight 11 as well. "He was a true friend and his kindness and devotion will be deeply missed," MRV President and CEO Noam Lotan said. "Our thoughts and prayers are with Edmund's family, friends, and colleagues and all the families that suffered personal losses during this tragedy."

Genzyme Corp. (GENZ: Research, Estimates) said its senior vice president of government relations and company officer, Lisa Raines, was among the passengers on board American Airlines Flight 77. "Lisa was a great friend and a brilliant colleague. She was a tremendous advocate for this company and for the biotechnology industry, who worked tirelessly and effectively in Washington to ensure that the best medicines reached patients," said Genzyme Chairman and CEO Henri A. Termeer. "We will greatly miss her."

Heinrich Kimmig, President, CEO of BTC Technologies

European companies also suffered losses in the attacks. BCT Technology AG's president and chief executive, Heinrich Kimmig, and the company's director of development, Klaus Bothe, died aboard a hijacked United Airlines flight.

In addition to being executives, many of the lost are parents and spouses. James Hayden, Netegrity Inc.'s (NETE: Research, Estimates) chief financial officer, was a passenger on United Airlines flight 175. He is survived by his wife and their two children. "Our sympathies are with his family and friends during this very difficult time," Netegrity Chairman and CEO Barry Bycoff.

TJX Cos. lost seven members of its staff. Neilie Casey, Tara Creamer, Robin Kaplan, Christine Barbuto, Linda George and Lisa Fenn Gordenstein all were passengers on American Airlines flight 11.

The company withheld the identity of the seventh employee at the request of her family, noting only that the woman was 42 years old and was assistant vice president of merchandising planning and allocation.